1. Field of the Invention
This invention pertains to the field of isocyanurate catalysts. More particularly this invention relates to the use of aminomethacrylate salts as isocyanurate catalysts.
2. Description of the Prior Art
The use of catalysts in preparing isocyanurate foams via the polymerization of a polyol polyisocyanate and optionally other ingredients in the presence of a blowing agent is well-known. The isocyanurate group formation catalyst is used to trimerize the isocyanate groups to form the isocyanurate linkages. The polyol essentially acts as a modifying or reactive plasticizing agent in the overall polymeric scheme since a polymer containing only isocyanurate groups is itself too friable. Thus, the isocyanurate foam contains both isocyanurate groups as well as urethane linkages, with said urethane linkages acting to plasticize the foam. Initially the reaction proceeds to give primarily a urethane quasi-prepolymer containing active isocyanate groups. Subsequently, the excess isocyanate reacts to form isocyanurate groups which ultimately produces a urethane-modified polyisocyanurate polymer.
Depending upon process condition utilized, both rigid and flexible polyisocyanurate foams may be prepared as well as the semi-flexible and semi-rigid types. Some main uses of the resultant foam include those of thermal insulation, and as building materials and the like. Examples of some prior art isocyanurate foams and methods of preparation are described in U.S. Pat. Nos. 3,745,133; 3,644,232; 3,676,380; 3,168,483; and 3,519,950, to name a few.
A number of prior art polyisocyanurate catalysts are known. However, in many instances these catalysts suffer from one or more deficiencies. Particularly, while useful in promoting trimerization of the isocyanate groups to isocyanurate polymer units the catalysts cause foam processing problems. Thus, in some instances such wellknown catalysts as potassium octoate and potassium acetate catalysts are overly temperature dependent. Thus, an unduly rapid end-cure is realized in some cases with such catalysts. That is, with a gradual rise in temperature, catalyst activity is increased in an excessive manner, making it difficult to properly control foam rise. Yet, in many cases, typified by slab formation, a uniform cure rate is particularly sought.
In other situations catalysts such as amine-type isocyanurate catalysts including amino hexaohydrotriazines are unduly slow with respect to their reactivity rate resulting in a lagging end-cure. As a result, the foam so cured is not sufficiently cured in time to properly handle. The soft "green" foam coming out of the machine will have a tendency to warp if, for example, panel board is being produced.
In still further cases use of many catalysts of this type such as xanthates, dithiocarbamates or volatile amines is accompanied by an odor problem of varying severity. A suitable isocyanurate catalyst therefore should be relatively odor-free and give a relatively long cream time with quick rise and task free times.
It would therefore be a considerable advance in the art if a new class of isocyanurate catalysts were discovered which overcomes the just discussed processing drawbacks whereby optimum foam cure rates could be achieved. It would be a further desirable achievement if such new class of isocyanurate chemical catalysts could be equally adopted in preparing isocyanurate foams useful as both rigid and flexible foams in making panels, slabs and sprayed foams.
It therefore is an object of the present invention to provide new odor-free isocyanurate catalysts which give a long cream time and short rise and tack free times. It is further an object of this invention to provide isocyanurate catalysts which can be utilized in preparing rigid, flexible, semi-rigid or semi-flexible isocyanurate foams. Another object of the present invention is to provide isocyanurate foams utilizing a new class of isocyanurate group formation catalysts. Finally, it is an object of the present invention to prepare modified polyisocyanurate foams which have suitable thermal stability, uniform cell structure, low friability, excellent adhesion and other sought-after properties, using a new class of isocyanurate catalysts.